Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS5876487 A
Publication typeGrant
Application numberUS 08/819,851
Publication dateMar 2, 1999
Filing dateMar 17, 1997
Priority dateMar 17, 1997
Fee statusPaid
Also published asCN1165912C, CN1250541A, WO1998041989A1
Publication number08819851, 819851, US 5876487 A, US 5876487A, US-A-5876487, US5876487 A, US5876487A
InventorsAndrew Christian Dahlgren, Robert Murray Rogers
Original AssigneeDonaldson Company, Inc.
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Computers
US 5876487 A
Abstract
An adsorbent filter including compression molded particulate adsorbent construction is provided. The compression molded particulate adsorbent construction contains a particulate adsorbent and a sufficient amount of binder to retain the particulate adsorbent in a non-free flowing form. The adsorbent filter preferably includes a compression molded particulate adsorbent construction as described, positioned within an outer, porous cover. Preferably the outer, porous cover includes expanded porous polytetrafluoroethylene. In certain preferred applications, the adsorbent filter is positioned within a housing defining an internal volume and including therein electronic component(s), such that the adsorbent filter protects the internal volume of the housing, and components therein, from damage. The typical application is as a disk drive adsorbent filter. A preferred method for preparing an adsorbent filter according to the present invention is provided.
Images(6)
Previous page
Next page
Claims(7)
We claim:
1. A combination comprising:
(a) a housing defining an internal volume including therein a computer disk drive to be protected; and,
(b) an adsorbent filter positioned within the housing internal volume; the adsorbent filter comprising: an outer, porous, adsorbent cover comprising a two-piece shell having a perimeter seal; and, a non-free flowing compression molded particulate adsorbent positioned within said two-piece shell;
(i) said compression molded particulate adsorbent comprising the result of compression molding a mixture including:
(A) 75-95%, by wt., particulate adsorbent; and,
(B) 5-25% binder;
wherein the particulate adsorbent, before compression molding, is selected from:
(1) powdered particulate adsorbent which goes through 100 mesh U.S.S.;
(2) granular particulate adsorbent which is 28-200 mesh U.S.S.; and
(3) mixtures thereof;
(ii) said binder being selected from: polyvinyl alcohol; starch; carboxymethyl cellulose; polyvinylpyrolidone; microcrystalline cellulose; dicalcium phosphate dihydrate; and, mixtures thereof;
(iii) said particulate adsorbent, prior to compression molding, comprising at least 70%, by wt., silica gel;
(iv) said non-free flowing compression molded particulate adsorbent resulting from a compression molding operation such that:
(A) the resulting compression molded particulate adsorbent has a density, of silica gel, which is greater than the bulk density of the silica gel used; and,
(B) the resulting compression molded particulate adsorbent has a total capacity for water vapor adsorption which is no less than a water vapor adsorption capacity of silica gel desiccant; of similar particle size, present in an amount equal to an amount contained within the particulate adsorbent but evaluated in a free-flowing, non-compression molded, form.
2. A combination according to claim 1 wherein:
(a) said adsorbent cover comprises expanded, porous, polytetrafluoroethylene.
3. A combination according to claim 2 wherein:
(a) said cover comprises polytetrafluoroethylene laminated to a scrim.
4. A combination according to claim 1 wherein:
(a) the compression molded particulate adsorbent has no external dimension which is less than 0.2 cm.
5. A combination according to claim 1 wherein:
(a) said particulate adsorbent, before compression molding, consists essentially of silica gel.
6. A combination according to claim 1 wherein:
(a) said particulate adsorbent, before compression molding, comprises a mixture of silica gel and activated carbon.
7. A method of inhibiting disk drive from vapor damage; said method comprising a step of:
(a) positioning within the disk drive a vapor adsorbent filter comprising: an outer, porous, adsorbent cover comprising a two-piece shell having a perimeter seal; and, a non-free flowing compression molded particulate adsorbent positioned within said two-piece shell;
(i) said compression molded particulate adsorbent comprising the result of compression molding a mixture including:
(A) 75-95%, by wt., particulate adsorbent; and,
(B) 5-25% binder;
wherein the particulate adsorbent, before compression molding, is selected from:
(1) powdered particulate adsorbent which goes through 100 mesh U.S.S.;
(2) granular particulate adsorbent which is 28-200 mesh U.S.S.; and
(3) mixtures thereof;
(ii) said binder being selected from: polyvinyl alcohol; starch; carboxymethyl cellulose; polyvinylpyrolidone; microcrystalline cellulose; dicalcium phosphate dihydrate; and mixtures thereof;
(iii) said particulate adsorbent, prior to compression molding, comprising at least 70%, by wt., silica gel; and,
(iv) said compression molded particulate adsorbent results from a compression molding operation such that:
(A) the resulting compression molded particulate adsorbent has a density, of silica gel, which is greater than the bulk density of the silica gel used; and
(B) the resulting compression molded particulate adsorbent has a total capacity for water vapor adsorption which is no less than a water vapor adsorption capacity of silica gel desiccant, of similar particle size, in an amount equal to an amount contained within the particulate adsorbent but evaluated in a free-flowing, non-compression molded form.
Description
FIELD OF THE INVENTION

The present invention relates to adsorbents. It particularly concerns provision of adsorbent filters that can be used in a variety of environments. The adsorbent filters are particularly well adapted for utilization in electronic equipment, for example in computer disk drives which are sensitive to humidity, organic vapors and/or acid gas.

BACKGROUND OF THE INVENTION

Adsorbent filters are widely utilized in such industries as the electronics industry and the pharmaceuticals industry. For example, in the computer industry, adsorbent filters are positioned within disk drives, to protect the disk drives from water vapor hydrocarbons and/or acid gases. Without such protection, these vapors can lead to stiction, corrosion and, ultimately, drive failure.

In general, adsorbent filters comprise a porous construction having positioned therein adsorbent. Arrangements presently widely used comprise granular or powdered adsorbent, for example desiccant and/or carbon adsorbent, enclosed within a pouch. Such an arrangement is described, for example, in U.S. Pat. No. 4,830,643 to W. L. Gore & Associates, Inc. The arrangements described in the '643 patent comprise a tubular container of porous polytetrafluoroethylene sealed at each end so as to enclose adsorbent particles. Among the materials described in the '643 patent as the adsorbent particles, are silica gel (SG), activated carbon, calcium sulfate, calcium carbonate, activated alumina and molecular sieve adsorbent.

Alternate constructions to those described in the '643 patent have been available from Donaldson Company, Inc. of Bloomington, Minn., the assignee of the present invention. The Donaldson constructions generally comprise a pouch comprising two sheets of polytetrafluoroethylene membrane, sealed to one another along a border or perimeter seal. Enclosed within the pouch is the particulate adsorbent material. In some constructions, a second pouch is enclosed within the first pouch, and the second pouch contains the adsorbent material. In either case, in the past in such constructions, the adsorbent material has typically comprised a loose, granular, flowable, solid material.

SUMMARY OF THE INVENTION

According to the present invention, an adsorbent filter construction is provided. The adsorbent filter construction generally comprises a compression molded particulate adsorbent construction contained within the inner volume of an outer porous cover. The compression molded particulate adsorbent construction generally comprises a mixture of particulate adsorbent and binder. A sufficient amount of binder is provided to keep the particulate adsorbent in a non-free flowing form. That is, the binder will retain the otherwise free-flowing granular or powdered adsorbent in a predetermined, rigid, shape. Thus, the compression molded particulate adsorbent construction comprises a brick, wafer or tablet which retains its form under normal handling and use conditions.

A preferred cover comprises expanded, porous, polytetrafluoroethylene. In certain preferred embodiments, the cover comprises polytetrafluoroethylene which has been laminated to a sufficient amount of thermoplastic polymer scrim, in an appropriate form or pattern, to allow for ultrasonic welding or heat sealing. Typically a polyolefin scrim, such as a spun bond polypropylene scrim, will be used to accomplish this.

The preferred compression molded particulate adsorbent construction comprises a mixture of particulate adsorbent (preferably powdered, i.e., which goes through 100 mesh; or, if granular, in a form which is preferably 28-200 mesh, United States Standard (U.S.S.)), mixed with a binder such as: polyvinyl alcohol (PVA); starch; carboxy methyl cellulose (CBC); polyvinylpyrolidone (PVP); microcrystalline cellulose (MCC); dicalcium phosphate dihydrate; or a mixture thereof.

Herein the term "U.S.S." refers to United States Standard screen, which is characterized by the number of wires per inch in the screen. For example, a 28 U.S.S. screen, comprises 28 wires per linear inch, with the wires evenly spaced. The term 28-200 mesh references material which passes through a 28 U.S.S. screen but is the fraction that does not pass through a 200 mesh U.S.S. screen. Thus, the term identifies a maximum and minimum particle size within the identified material. It is noted that the characterization is not intended to be absolute; for example, some particles may break or form powder and others may agglomerate to form larger sizes, before or after the screening. Rather, the term is meant to refer to its general use in the trade, which is merely to the screen fraction(s) selected for the composition. In general, it will be found that a definition of material by screen size is generally indicative of screen size for a great majority of the particles, both by number and weight.

When the particulate adsorbent used is a powder, preferably it is a particulate material which passes through 100 mesh. Most preferably, it is a fraction which predominantly comprises particles having a nominal (average) size greater than 7 microns. This is in part because when the nominal size of the particles is 7 microns or less, flow of the material through tabletting machines may be a problem. If the size is greater than 28 mesh, getting effective binding may be a problem.

The adsorbent material, as explained in further detail below, can be a wide variety of materials. For a majority of typical applications, it is perceived that the adsorbent material will be: desiccant (for water vapor adsorption); a form of activated carbon (for organic vapor adsorption or acid gas adsorption); or, a mixture of the two. The general term "adsorbent" as used herein is not meant to refer to any particular material or material for adsorption of any particular contaminant. More generally, the adsorbent may comprise: silica gel; untreated activated carbon; chemically treated activated carbon for adsorption of acid gas (typically chemical treatments being with potassium carbonate, calcium carbonate or sodium carbonate); molecular sieve; activated alumina; or, mixtures thereof. Herein the term "carbon adsorbent" or variants thereof is meant to include activated carbon and chemically treated activated carbon, unless otherwise specified.

According to the present invention, a combination is provided which comprises a housing defining a cavity or internal volume, for example including therein electronic component(s), and at least one adsorbent filter, as previously described. Typically, the volume will be the inside of a disk drive. The filter is positioned within the housing internal volume to adsorb vapors (for example moisture vapor and/or organic vapor) therein. The housing and electronic component(s) may comprise, for example, a computer disk drive.

Herein the terms "adsorbent" and "adsorb" are not intended to be limiting with respect to the manner or mechanism of vapor entrapment. That is, the terms are intended to refer to any mechanism of entrapment whether it be adsorption, absorption or some other mechanism.

Also according to the present invention, a method of protecting an electronic component, such as a computer disk drive, from damage due to the presence of vapors therein is provided. The method generally comprises positioning within the electronic component at least one adsorbent filter as described above. Alternatively, the filter could be used in a container for pharmaceuticals.

Also according to the present invention a method of preparing an adsorbent filter is provided. The method generally comprises compression molding a composition comprising a mixture of at least particulate adsorbent (powdered or granular), or mixture of adsorbent, and binder(s). The mixture may further comprise lubricant. A preferred lubricant for such a construction would be powdered PTFE, for example as available under the trade designation TeflonŽ from DuPont, of Wilmington, Del.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a filter construction according to the present invention;

FIG. 2 is a cross-sectional view taken along line 2--2, FIG. 1;

FIG. 3 is a perspective view of an internal component of the construction shown in FIG. 1;

FIG. 4 is an exploded perspective view of an environment of use for the filter construction depicted in FIG. 1;

FIG. 5 is a first graph presenting data described in the Experimental section; and,

FIG. 6 is a second graph presenting data described in the Experimental section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

I. Further Comments Regarding Granular Desiccant

Adsorbent filters, especially those which are to be for use within electronic components, for example to protect: computer disk drives; cellular phones; circuit boards; VCR's; TV's; and headlight assemblies, must be relatively small in size. Generally they should occupy a volume no greater than approximately 262 cubic centimeters (cc or cm3), and typical ones for disk drives, depending upon the specific system of concern, will occupy volumes of approximately 0.008-262 cm3, more typically 0.26 to 18 cm3.

Conventional arrangements generally comprise a pouch, formed within the size limitations defined, having enclosed therein adsorbent in a flowable powder or granular form. A widely held conventional belief has been that the high surface area provided by the flowable granular form, was necessary and desirable for effective adsorbent operation. This is described, for example, in U.S. Pat. No. 4,830,643 at col. 1, lines 25-36.

While arrangements using flowable particulate material have been widely used, they are subject to certain inherent problems. For example, it is difficult to precisely control the adsorbent quantity placed in any given pouch, when a flowable granular material is used. Also, the quantity that can fit within any given volume is generally limited by the bulk density of the granular (i.e., free flowing) adsorbent.

In addition, for typical systems, after the granular material is positioned within an outer pouch or protective construction, some portion of the pouch or protective construction must be sealed. If any of the powder or granular material is positioned where the sealing is to occur, the seal may be compromised and/or difficult to obtain. This can lead to material waste and product failure; and, in some instances, contamination of the environment in which the adsorbent filter is eventually placed, by the powdered or granular desiccant material.

In addition, manufacturing or component assembly in many instances must be conducted in a clean room environment. It would be preferred, if possible, to avoid risk of loose powder or granular materials, i.e., flowable materials, in such an environment.

II. An Embodiment

Attention is now directed to FIGS. 1-3, which show a first embodiment of an adsorbent filter according to the present invention; and, FIG. 4, which shows a combination or embodiment of use.

Referring first to FIG. 4, an enclosed volume for use, in particular a computer disk drive 1, is depicted. The disk drive 1 of FIG. 1 is depicted in exploded view, and shows a housing 2 comprising cover 3 and base 4. In base 4, typically comprising a casting such as an E-coated aluminum casting, is positioned the disk drive components 6 (hardware or electronic componentry). Within volume 7, defined by base 4 and cover 3 when assembled, it is necessary and/or desirable to provide for vapor control during equipment use and temperature cycling. This vapor control is provided by filter construction 10, for example including desiccant (for moisture vapor control) and/or activated carbon for organic vapor control or acid gas control, as described. Of course alternate or additional adsorbents can be used.

In some instances, the base or casting of a computer disk drive is formed with a receiving space or slot therein, in which the filter construction 10 is loosely positioned, during assembly. The side walls and cover associated with the slot would tend to retain the filter construction 10 in place, as desired, through product use. In some alternate arrangements, an adhesive is positioned on a flat surface of the filter construction 10, and the construction 10 is secured in place thereby. When such is the case, generally a low outgassing, permanent, acrylic, pressure sensitive adhesive (PSA) is used. Usable adhesives are those available from 3M Company of St. Paul, Minn. under the designation 467MS.

As a third alternative, in some instances a plastic housing or frame which can be secured within the casting or base 4, and which is sized to loosely receive the filter construction 10 therein, is used.

In general, as the three alternatives described above indicate, all that is required is an appropriate arrangement to retain the filter construction 10 from interfering with operation of the electronic componentry 6, in use. Arrangements which allow relatively free air flow movement into, and through, the filter construction 10, by diffusion, are generally preferred.

Attention is now directed to FIGS. 1-3, in which filter construction 10 is depicted in detail. In FIG. 1, filter construction 10 is shown in perspective. FIG. 2 depicts the construction 10 in cross-section. In FIG. 3, an internal component of construction 10 is depicted.

Referring to FIG. 1, filter construction 10 includes an outer cover, casing, pouch or shell 12. Preferably the outer cover, casing, pouch or shell 12 is formed from a stable, porous material. As a result, vapors to be adsorbed can pass therethrough, via diffusion.

Preferred materials and porosities for the cover 12 are provided hereinbelow, in a detailed description of preferred components. In general what is necessary and desirable is an appropriate porosity for passage therethrough (via diffusion) of vaporous materials, for example, water vapor, organic vapors, acid gas, etc., the presence of which is/are to be controlled by the adsorbent material positioned within the pouch. In preferred arrangements such as the one depicted, except perhaps along a perimeter seal region, discussed below, the outer casing pouch or shell 12 is porous throughout its surface area.

Still referring to FIG. 1, the particular cover or casing 12 depicted comprises two shell pieces 15, 16, secured to one another along a perimeter seal. Shell piece 15 is flat, and forms a cover 17. Shell piece 16 is formed in a bowl or receptacle shape 18, with an outer flange 19. Shell piece 15 is secured to the outer flange 19 of shell piece 16, by perimeter seal 20. As a result, the adsorbent material is encapsulated by the cover 12. Preferred methods of forming the perimeter seal 20 are described below. Herein, the material from which the cover 12 is formed may sometimes be referred to as the encapsulating material, with the cover sometimes referred to as the encapsulating construction.

In general, shell piece 15 and shell piece 16 define an interior pouch or volume 24, FIG. 2, in which is received adsorbent construction 25. The adsorbent construction 25 is not provided in the form of flowable powder or particulate. Rather, adsorbent construction 25 comprises previously flowable particulate (powder or granules) which has been secured into a tablet, wafer or brick form. Preferred methods and formulations for accomplishing this are described below. In FIG. 3, adsorbent construction 25, comprising tablet, wafer or brick 29 is depicted. The construction 25 will retain its form, shape or integrity during normal handling.

Construction in the arrangement shown in FIGS. 1-3 would proceed as follows. Tablet or brick 29 would be formed from flowable particulate material, for example granular desiccant (moisture control) and/or activated carbon or treated activated carbon (organic vapor control and/or acid gas control), by procedures such as those described below. In general, granular or powdered (i.e., particulate) adsorbent material would be mixed with an appropriate amount of binder and then be compression molded, to form the brick (tablet or wafer) 29. If desired, additional material could be provided in the mixture, before compression molding, to provide for some organic vapor adsorption (and control) by construction 10.

Preferably, powdered or granular (particulate) binder is used. In some instances, it may be desirable to mix the binder and adsorbent under conditions in which the binder is moist, so that the moisture will operate as a temporary binder to help secure the binder material to the adsorbent particles. This is described hereinbelow, when a preferred process for production is described.

Shell piece 16 can be formed from an appropriate material such as described below.

In general, the cavity or volume in shell piece 16, which receives the brick, can be formed simultaneously with the positioning of the brick (tablet or wafer) 29 therein. In general, a sheet of the material from which shell piece 16 is formed would be positioned over an appropriately sized mold or cavity. The brick (wafer or tablet) 29 would then be pressed into the sheet of shell piece material, and into the cavity, with the sheet positioned between the brick and the mold cavity. This will mold the shell piece 16 with the cavity therein, at the same time the brick (tablet or wafer) 29 is put therein. In general, with the preferred materials selected below, such an operation can be readily achieved. In the alternative, a press can be used to pre-form the shell piece 16, before the brick, tablet or wafer 29 is positioned therein.

The resulting arrangement, comprising shell piece 16 with brick (tablet or wafer) 29 therein would then be covered by shell piece 15, and perimeter sealed, for example by ultrasonic welding or heat sealing.

In general, it is foreseen that the mold or casting into which the brick 29 and shell piece 16 are pressed, during assembly, will be used as a weld nest, during application of the cover sheet 15 and during the ultrasonic welding or heat sealing operation. This will facilitate convenient, rapid manufacture.

Disadvantages of handling flowable particulate material, during assembly of the filter construction, are thus avoided. Also, in some instances when preferred techniques such as those described hereinbelow are utilized for formation of the tablet or brick 29, the amount of adsorbent per unit volume can exceed the bulk density of the adsorbent in its free flowing state. As will be apparent from experimental results reported below, effective operation as a filter is accomplished in spite of the fact that a binder has been mixed with the adsorbent material and in spite of the fact that the adsorbent is formed into a brick, tablet or wafer (i.e., predetermined and not free flowing) form.

In general, in many instances it will be preferred to wash or clean the construction 10, before it is positioned within the computer disk drive. Any method which achieves a desired level of cleanliness in the product for the end use, is usable. This will generally be based on the preferences of the particular manufacturer, for example disk drive manufacturer, involved. In general it is foreseen that conventional techniques involving ultrasonic washes with deionized water and various detergents will be desirable. Multi-stage washing and variations depending on the particular level of contaminant control desired for any given application, are feasible when the preferred materials described herein are used. Such washing techniques should have no negative effect on the operation of the construction 10 as the adsorbent filter, especially when the construction 10 is prepared from the preferred materials described below.

III. Usable and Preferred Material

A. The Pouch or Encapsulating Material

In general, the material used to form the pouch, cover or encapsulating construction is preferably sufficiently porous to allow movement of air, water vapor and, if appropriate, organic vapor therethrough, freely, while at the same time appropriately enclosing the adsorbent construction. Preferred physical specifications for the pouch, cover or encapsulating material are:

Thickness range: 0.0005-0.050 inches

MVTR (Moisture Vapor 950 g/m2 /24 Hour Minimum per Transmission Rate): ASTM E96 Wet Cup Method

Particle Efficiency: 99.99% Minimum on 0.3 micron at 10.5 fpm

Pore Diameter: 0.1-2.0 micron

It is also preferred that the material be relatively strong, resistant to tear or break, inexpensive, and readily available. Preferred materials comprise expanded, porous, polytetrafluoroethylene (PTFE) materials. The PTFE may be obtained from a variety of suppliers, or manufactured using known techniques. Usable PTFE is available from Tetratec, a division of Donaldson Company, Inc. of Bloomington, Minn.; and, from W. L. Gore & Associates, Inc., of Newark, Del. Preferably it is obtained in a form laminated to a spun bond polypropylene or similar material to facilitate heat bonding or ultrasonic welding.

Expanded porous polytetrafluoroethylene made according to the procedures described in U.S. Pat. Nos. 4,110,392; 4,187,390; and, 3,953,566 may be used. However, alternate materials are usable, as long as the general physical requirements are met. The three identified patents are incorporated herein by reference.

For the particular construction shown in FIGS. 1-3, it is necessary that the material provide a perimeter seal. It is preferred, then, that the porous PTFE material be provided in a form such that it can be sealed to itself, to form the perimeter seal or weld. A preferred technique for accomplishing this, is to apply to the PTFE material, on the side to be sealed, a layer of a thermoplastic polymer (for example a polyolefin such as a polypropylene). A fibrous material such as a spun bond scrim can be used. Such a material will not substantially modify the porosity characteristics of the construction 12, but will provide for an overall construction that can be sealed to itself, where the polypropylene is present. That is, the thermoplastic polymer side of the sheet or laminate construction can be sealed to itself, using ultrasonic welding techniques, for example. From PTFE suppliers such as those identified, a suitable film film comprising PTFE laminated to a spun bond polypropylene scrim is generally available.

For typical arrangements used with computer disk drives, a variety of geometric configurations may be desirable. Generally, rectangular wafers or bricks will be preferred (i.e., square or rectangular when viewed in the plane view toward any side).

In general it will be preferred that the materials used for the construction 10 not contain detectable levels (by conventional NVR/FTIR analysis) of silicones, amides or DOP (dioctyl plithalate). It is also preferred that there be no detectable offgassing of hydrocarbons and other harmful contaminants to a disk drive, as determined by headspace GC/MS @ 105° C. for 24 hours. The characterized polytetrafluoroethylene materials, with polypropylene scrim applied thereto for sealing, provide for this. It is noted that these latter requirements are desirable for the overall construction, and thus apply to the material positioned within the pouch, casing or shell construction as well. The preferred materials defined in the next section meet these requirements.

Herein the term "NVR" refers to nonvolatile residue analysis, and the term "FTIR" refers to conventional fourier transform infrared analyses. The term "GC/MS" refers to gas chromatography/mass spectrometry, using conventional techniques.

B. The Adsorbent Brick, Tablet or Wafer

The adsorbent brick, tablet or wafer, enclosed within the pouch, is preferably the result of compression molding or otherwise forming a mixture of flowable, granular powder material and binder, into a molded, stable, wafer, brick or tablet. That is, sufficient binder is used to retain the compression molded particulate adsorbent construction in a non-free flowing form. By the term "non-free flowing" in this context, it is meant that the individual particles or granules from which the construction (brick, tablet or wafer) is formed are sufficiently bound that they do not separate during normal handling. As indicated above, the composition, prior to compression molding, may include any of a variety of selected adsorbents (or mixture) for the vapor control desired; i.e., moisture vapor, organic vapor, and/or acid gas vapor control.

For typical operation, a material which is stable and adsorbs within a temperature range of -40° C. to 100° C. will be preferred. Preferably powdered (passes through 100 mesh U.S.S.) or granular (28-200 mesh) adsorbent is used. A nominal (average) particle size of about greater than 7 microns is typical and desirable. Examples of usable materials are identified in the materials table below.

Generally preferred binders are, prior to application, dry, powdered or granular binders, which can be readily mixed with the adsorbent. As indicated below, in certain preferred operations, the solid, powdered or granular, binder and the adsorbent are mixed together, in the presence of liquid temporary binder to facilitate coating, and then are dried. It is preferred to avoid a binder material which will tend to completely coat the adsorbent, blocking it from effective operation in the overall assembly. Preferred binder materials are listed in the table of preferred materials below.

Preferably the composition of the tablet, brick or wafer comprises approximately 50-98%, by weight, adsorbent (more preferably a majority, for example 75-95%, most preferably approximately 80%); and, about 2-50%, by weight, binder (more preferably a minority, for example 5-25%, most preferably approximately 20%). In some instances, it may be desirable to include a small amount of lubricant such as PTFE (TeflonŽ powder) within the composition, in order to facilitate mold release. When such is used, preferably no more than about 10%, and more preferably less than about 3% of the composition, comprises added lubricant. If a lubricant is used, preferably a minimum amount effective to accomplish a desirably reproducible mold release, is used.

The brick, wafer or tablet can be formed using a variety of compression molding or tablet-forming techniques. Generally all that is required is sufficient pressure and/or heat to ensure brick integrity under ordinary handling and manufacturing conditions. A compression such that a given volume contains about 0.8-1.75 times (preferably 1 to 1.75 times, most preferably greater than 1 time), by weight, adsorbent by comparison to the amount of adsorbent that would occupy the same volume if it were left in a granular, free-flowing state, is generally adequate and desirable. To accomplish this, such techniques as conventional tabletting are readily adaptable. Generally tabletting pressures on the order of 12,700 to 25,500 psi will suffice. It may be possible to use lower pressures by optimizing the formulation, or modifying the binder, for any selected application and geometry.

When the solids primarily (i.e., >70% by wt.) comprise silica gel for operation as a desiccant (i.e., water adsorption), generally a minimum effective bulk density of at least 0.61 g/cc (grams/cubic centimeter) after molding is desirable. Preferably sufficient compression occurs to get a density greater than 0.85 g/cc, and preferably about 0.92 g/cc.

Preferably the material is molded so that the resulting predetermined shape has no dimension which is less than 0.20 cm, and more preferably has no dimension which is less than about 0.51 cm. This will help ensure structural stability to the compression molded item. Preferably, for typical uses in electronic components, an overall bulk volume for the compression molded item within the range of about 0.008 to 262 cm3 will be preferred, more typically 0.26 to 18 cm3. In this context, the term "bulk volume" is meant to refer to the volume calculated from either the compression mold cell or the outside dimensions to the resulting compression molded product. For a typical disk drive filter, a "brick" approximately 3.1 cm long, and approximately 0.6 cm thick in one dimension and approximately 0.5 cm thick in the other (the product having flat sides) is usable.

In the following paragraphs, a usable technique for manufacturing the brick, wafer or tablet is provided. From this method, a variety of general applications will be apparent. In the method description the "% by weight" figures are based upon total weight of dry materials in the final brick, wafer or tablet 29 (FIG. 3). The wt. of any later applied cover is not included in this description.

First, a dry mixture would be prepared comprising 63% a by weight silica gel (28-200 mesh silica gel) with about 10.5% polyvinyl alcohol powder (PVA, Air Products'Air Vault 203S). These materials would be mixed with water or another liquid, with 1 part of water for every 2 parts silica gel, and then are air dried. The water acts as a temporary processing binder and helps to enhance the coating of the binder over the silica gel.

The dry material would be screened with a 30-mesh screen to reduce lumps. To this would be added about 24% microcrystalline cellulose (MCC, FMC Lattice NT-050 or NT-105). To the mixture would also be added 2.5% TeflonŽ powder (DuPont Zonyl MP-1100) as lubricant.

The tablet would then be formed by using a conventional tabletting machine at pressures of 12,700-25,500 psi.

Typical tablet sizes would be as follows:

Length: 0.38 cm-10.16 cm

Width: 0.38 cm-10.16 cm

Thickness: 0.38 cm-2.54 cm

Using a water soluble PVA formulation has a variety of advantages. For example, the mix is free flowing which allows for high speed tablet making. Also, PVA powder mixes well with silica gel. The composition of PVA powder is acceptable for disk drive applications. That is it does not release volatiles that are undesirable within disk drives. The method described above is advantageous in part because it avoids the use of alcohol solvents. As a result, less contamination to electronic equipment is likely.

In Table I below, some usable materials for the tablet are identified.

              TABLE I______________________________________USABLE MATERIALS FOR TABLETComponent   Function      Supplier(s) and Sample Products______________________________________Silica Gel   Water Vapor   Grace Davison (Grade 11 or Syloid   Adsorption    63)                 Baltimore, MD 21203-2117;                 Fuji Sylisia (Type A or Type B)                 Portland, OR 97204Activated   Adsorption of organic                 Barnebey and Sutcliffe (209C;Carbon  vapors, hydrocarbons                 209C KINA)   and/or acid gasses                 Columbus, OH 43216Micro-  Binder        FMC (Lattice NT-050 or NT-006)crystalline           Philadelphia, PA 19103CelluloseTeflon  Lubricant     DuPont (Zonyl MP 1100)Powder                Wilmington, DE 19805Polyvinyl   Binder        Air Products (Airvol 203S)Alcohol               Allentown, PAStarch  Binder        ADM (Clineo 718)                 Clinton, IACarboxyl   Binder        Hercules (Aqualon 7MX)Methyl                Wilmington, DE 19894CellulosePolyvinyl-   Binder        GAF Chemicals Corporationpyrrolidone           (Plasdone) Wayne, NJ 07470Dicalcium   Binder        Rhone Poulenc (DI-TRB)Phosphate             Shelton, CTDihydrate______________________________________
Experimental

Objective

The objective of this study was to compare the adsorption characteristics of Silica Gel Tablets according to the invention with the present Adsorbent Pouches (using loose granular silica gel) supplied in the past by Donaldson Company, Inc. (the assignee of the present invention) to the disk drive industry.

Procedure

The tablets were formed using a process as generally described above and detailed further below. The tabletting pressure was approximately 25,000 using a hand tabletting. The following samples were included in this study:

______________________________________Part Number  Description______________________________________11 80/20 (A) Tablet with 80% Davison Grade 11 Silica        Gel by Weight; 20% Lattice 006        Microcrystalline Cellulose (MCC); 3        tablets per weighing pan; each was 7 mm        (millimeters) dia., 2.7 mm thick63 80/20 (B) Tablet with 80% Davison Syloid 63 Silica        Gel by Weight; 20% Lattice 006 MCC; 3        samples per weighing pan; each was 7 mm        dia., 1.8 mm thick11 70/30 (C) Tablet with 70% Davison Grade 11 Silica        Gel by Weight; 30% Lattice 006 (MCC); 3        tablets per weighing pan; each was 7 mm        dia., 2.7 mm thick63 70/30 (D) Tablet with 70% Davison Syloid 63 Silica        Gel by Weight; 30% Lattice 006 (MCC); 3        tablets per weighing pan; each 7 mm dia.,        1.8 mm thick63 50/50 (E) Tablet with 50% Davison Syloid 63 Silica        Gel by Weight; 50% Lattice 006 (MCC) ; 2        tablets per weighing pan; each 7 mm dia.,        1.8 mm thickP53-7365 (F) Present Adsorbent Pouch Supplied to the        Disk Drive Industry by Donaldson Company,        Inc. as Part P53-7365 (Baseline); 1 sample        per weighing pan; pouch length 29 mm,        pouch width 12.7 mm, pouch thickness 6.4        mm.______________________________________

A sample (called "11 PVA" or "G") was also made comprising: 63%, by wt., Davison Grade 11 silica gel; 10.5% Air Products'Airvol 203S PVA; 24% Lattice NT-050 MCC; and 2.5% DuPont Zonyl MP-1100 Teflon powder. Its diameter was 12.7 mm and it had a thickness of 0.28 mm. Only one tablet of this was used, per weighing pan.

Davison Grade 11 is a 28-200 mesh silica gel, while Davison Syloid 63 is a 7 micron powder form of silica gel. All samples were run in duplicate except P/N 63 50/50 (E) which had a limited sample availability. Thus, data A1 and A2 are for the two runs of material A, etc.

Sample Preparation

Each tablet using MCC only was prepared by weighing out the raw material ratios as called for above. The samples were then formed into tablets on a hand tablet press. The pressure applied during tablet forming was approximately 25,000 psi for MCC.

For tablets using a mixture of MCC, PVA, and Teflon, the following procedure was used for tablet forming:

1) Mix 6 parts Davison Grade 11 Silica Gel with 1 part Air Products Airvol 203S PVA.

2) Take the mixture from (1) and add 1 part of water for every 2 parts of silica gel.

3) Air dry the mixture.

4) Screen the mixture with a 30 mesh screen to reduce lumps.

5) Add and mix FMC Lattice NT-050 MCC such that the final mixture will contain 24% MCC by weight.

6) Add and mix DuPont Zonyl MP-1100 Teflon Powder such that the final mixture will contain 2.5% by weight.

7) Form tablets using 17,800 to 25,500 psi on a hand tablet press.

The following procedure was used for this analysis:

1) Each sample (1,2 or 3 tablets as indicated above) was placed into a labeled aluminum pan for identification purposes. The P53-7365 baseline was tested as supplied with a PTFE outer cover. The other samples were tested without encapsulating covers.

2) The samples were dried at 105° C. for 15 hours.

3) The samples were removed from the oven, individually sealed in vapor barrier packaging and allowed to cool to ambient conditions.

4) A Tenney temperature and humidity chamber was programmed to maintain 50% RH (Relative Humidity) and 21.1° C. and allowed to equilibrate.

5) Each sample was then removed from its vapor barrier package and weighed. This weight was recorded as the dry weight. Ambient exposure time was minimized to ensure accurate dry weights.

6) The samples were then placed into the temperature and humidity chamber and the time was recorded as the start time.

7) Each individual sample was removed from the chamber and weighed periodically. The time was recorded for each weight measurement. Ambient exposure time was minimized to ensure meaningful weight measurements.

8) Weight measurements were taken for each part until equilibrium was reached.

9) The weight of adsorbent was determined for each part based upon the formulation and the dry weight or direct measurement.

Again, for some samples, as indicated in the table above, 2 or 3 individual tablets made up the sample.

Data Analysis/Background

The weights were compiled as a function of time for each sample. The dry weights were subtracted from each measurement with the difference assumed to be water vapor adsorption. The mass of water vapor adsorbed was calculated as a function of time for each sample and then normalized per mass of dry silica gel and adsorbent volume. The normalized adsorption curves were then graphed as a function of time to infer adsorbent performance. The graphs allow a direct comparison between the silica gel tablets and the P53-7365 (F1 and F2) baseline. The data collected, for all but 11 PVA or G, is found in Tables II, III and IV below.

                                  TABLE II__________________________________________________________________________Raw Data (Sample wt. (Gram)__________________________________________________________________________Sample name  Sample #__________________________________________________________________________11 80/20 (1)  A1   1.3246           1.3460               1.3622                   1.3725                       1.3799                           1.3849                               1.3894                                   1.3921                                       1.3936                                           1.3936                                               1.395111 80/20 (2)  A2   1.3406           1.3656               1.3788                   1.3903                       1.399                           1.4037                               1.408                                   1.4115                                       1.4121                                           1.4117                                               1.412463 80/20 (1)  B1   1.2252           1.2416               1.254                   1.262                       1.2666                           1.2677                               1.2689                                   1.2704                                       1.2702                                           1.2693                                               1.269963 80/20 (2)  B2   1.4704           1.4818               1.4882                   1.4948                       1.4979                           1.4985                               1.4992                                   1.4997                                       1.4997                                           1.4994                                               1.499911 70/30 (1)  C1   1.6509           1.6686               1.6858                   1.6981                       1.7049                           1.7086                               1.7126                                   1.7154                                       1.7157                                           1.7156                                               1.71611 70/30 (2)  C2   1.6508           1.6704               1.6864                   1.6941                       1.7047                           1.7087                               1.712                                   1.7153                                       1.716                                           1.7154                                               1.716563 70/30 (1)  D1   1.5338           1.5505               1.56                   1.5657                       1.5705                           1.5720                               1.5740                                   1.5753                                       1.5751                                           1.5745                                               1.574763 70/30 (2)  D2   1.4628           1.4732               1.4797                   1.4837                       1.4870                           1.4883                               1.4892                                   1.490                                       1.4898                                           1.4983                                               1.489663 50/50 (1)  E    1.4935           1.5007               1.5065                   1.5093                       1.5115                           1.513                               1.5139                                   1.5145                                       1.515                                           1.5145                                               1.5144P537365  F1   2.2749           2.2997               2.325                   2.3444                       2.3628                           2.3762                               2.3895                                   2.4008                                       2.4081                                           2.4122                                               2.4156Baseline (1)P537365  F2   2.2992           2.323               2.3509                   2.3687                       2.3922                           2.4037                               2.4137                                   2.4272                                       2.4328                                           2.4356                                               2.4421Baseline (2)  time(mins)       0   30  63  96  131 164 194 224 255 285 316__________________________________________________________________________               Sample name                      Sample #__________________________________________________________________________               11 80/20 (1)                      A1   1.3947                               1.394                                   1.3988                                       1.3978                                           1.3973                                               1.3982               11 80/20 (2)                      A2   1.4134                               1.4139                                   1.4192                                       1.418                                           1.4176                                               1.4181               63 80/20 (1)                      B1   1.2702                               1.2698                                   1.2715                                       1.2708                                           1.2704                                               1.2716               63 80/20 (2)                      B2   1.4999                               1.4994                                   1.5002                                       1.4997                                           1.4996                                               1.5000               11 70/30 (1)                      C1   1.7172                               1.717                                   1.7211                                       1.7203                                           1.7199                                               1.7208               11 70/30 (2)                      C2   1.717                               1.7169                                   1.7219                                       1.7205                                           1.7203                                               1.7209               63 70/30 (1)                      D1   1.5754                               1.5751                                   1.5761                                       1.5753                                           1.5754                                               1.5759               63 70/30 (2)                      D2   1.4895                               1.4897                                   1.4908                                       1.4899                                           1.4900                                               1.4905               63 50/50 (1)                      E    1.5147                               1.5146                                   1.5155                                       1.5149                                           1.5149                                               1.5151               P537365                      F1   2.4229                               2.4302                                   2.4813                                       2.4749                                           2.4767                                               2.4795               Baseline (1)               P537365                      F2   2.4507                               2.4563                                   2.5064                                       2.5053                                           2.5046                                               2.5064               Baseline (2)                      time(mins)                           346 377 1244                                       1274                                           1305                                               1364__________________________________________________________________________

                                  TABLE III__________________________________________________________________________Water Vapor Adsorbed (Gram)__________________________________________________________________________  Sample #Sample name  time(mins)       0   30  63  96  131 164 194 224 255 285 316__________________________________________________________________________11 80/20 (1)  A1   0   0.0214               0.0376                   0.0479                       0.0553                           0.0603                               0.0648                                   0.0675                                       0.069                                           0.069                                               0.070511 80/20 (2)  A2   0   0.0250               0.0382                   0.0497                       0.0584                           0.0631                               0.0674                                   0.0709                                       0.0715                                           0.0711                                               0.071863 80/20 (1)  B1   0   0.0164               0.0288                   0.0368                       0.0414                           0.0425                               0.0437                                   0.0452                                       0.045                                           0.0441                                               0.044763 80/20 (2)  B2   0   0.0114               0.0178                   0.0244                       0.0275                           0.0281                               0.0288                                   0.0293                                       0.0293                                           0.029                                               0.029511 70/30 (1)  C1   0   0.0177               0.0349                   0.0472                       0.054                           0.0577                               0.0617                                   0.0645                                       0.0648                                           0.0647                                               0.065111 70/30 (2)  C2   0   0.0196               0.0356                   0.0433                       0.0539                           0.0579                               0.0612                                   0.0645                                       0.0652                                           0.0646                                               0.065763 70/30 (1)  D1   0   0.0167               0.0262                   0.0319                       0.0367                           0.0382                               0.0402                                   0.0415                                       0.0413                                           0.0407                                               0.040963 70/30 (2)  D2   0   0.0104               0.0169                   0.0209                       0.0242                           0.0255                               0.0264                                   0.0272                                       0.027                                           0.0265                                               0.026863 50/50 (1)  E    0   0.0072               0.0130                   0.0158                       0.018                           0.0195                               0.0204                                   0.021                                       0.0215                                           0.021                                               0.0209P537365  F1   0   0.0248               0.0501                   0.0695                       0.0879                           0.1013                               0.1146                                   0.1259                                       0.1332                                           0.1373                                               0.1407Baseline (1)P537365  F2   0   0.0238               0.0517                   0.0695                       0.093                           0.1045                               0.1145                                   0.128                                       0.1336                                           0.1364                                               0.1429Baseline (2)__________________________________________________________________________                      Sample #               Sample name                      time(mins)                           346 377 1244                                       1274                                           1305                                               1364__________________________________________________________________________               11 80/20 (1)                      A1   0.0701                               0.0694                                   0.0742                                       0.0732                                           0.0727                                               0.0736               11 80/20 (2)                      A2   0.0728                               0.0733                                   0.0786                                       0.0774                                           0.077                                               0.0775               63 80/20 (1)                      B1   0.045                               0.0446                                   0.0463                                       0.0456                                           0.0452                                               0.0464               63 80/20 (2)                      B2   0.0295                               0.029                                   0.0298                                       0.0293                                           0.0292                                               0.0296               11 70/30 (1)                      C1   0.0663                               0.0661                                   0.0702                                       0.0694                                           0.069                                               0.0699               11 70/30 (2)                      C2   0.0662                               0.0661                                   0.0711                                       0.0697                                           0.0695                                               0.0701               63 70/30 (1)                      D1   0.0416                               0.0413                                   0.0423                                       0.0415                                           0.0416                                               0.0421               63 70/30 (2)                      D2   0.0267                               0.0269                                   0.028                                       0.0271                                           0.0272                                               0.0277               63 50/50 (1)                      E    0.0212                               0.0211                                   0.022                                       0.0214                                           0.0214                                               0.0216               P537365                      F1   0.148                               0.1553                                   0.2064                                       0.2 0.2018                                               0.2046               Baseline (1)               P537365                      F2   0.1515                               0.1571                                   0.2072                                       0.2061                                           0.2054                                               0.2072               Baseline (2)__________________________________________________________________________

              TABLE IV______________________________________Volume Calculation    Sample  #       Diam  radius                                height                                      volumeSample name    #       Tablets (in)  (in)  (in)  (in3______________________________________11 80/20 (1)    A1      3       0.284 0.142 0.106 0.020111 80/20 (2)    A2      3       0.289 0.1445                                0.109 0.021463 80/20 (1)    B1      3       0.288 0.144 0.072 0.014163 80/20 (2)    B2      2       0.287 0.1435                                0.07  0.009111 70/30 (1)    C1      3       0.289 0.1445                                0.105 0.020711 70/30 (2)    C2      3       0.289 0.1445                                0.107 0.021063 70/30 (1)    D1      3       0.291 0.1455                                0.071 0.014263 70/30 (2)    D2      2       0.289 0.1445                                0.07  0.009263 50/50 (1)    E       2       0.287 0.1435                                0.07  0.0091P537365  F1              0.4335                          0.2445                                1.0775                                      0.0835Baseline (1)P537365  F2              0.4365                          0.261 1.0775                                      0.0909Baseline (2)______________________________________

Results/Discussion

FIG. 5 shows the rate of water vapor adsorption for each sample normalized per mass of dry silica gel. As shown in FIG. 5, the rate of adsorption for the silica gel tablets is greater than that of the P53-7365(F1 and F2) baseline. The final capacity of each sample normalized per mass of dry silica gel ranges from 25-30%. The range is likely a result of variability in the mixture of silica gel to binder for each sample. Silica gel in bulk form would be expected to adsorb approximately 28.75% of its weight at the conditions specified. Therefore, the tablet process does not negatively affect the water vapor adsorption of the silica gel.

FIG. 6 outlines the water vapor adsorption normalized per unit volume. As shown in FIG. 6, the silica gel tablets outperform the P53-7365(F1 and F2) baseline in terms of capacity per unit volume. This characteristic is especially useful in Disk Drive applications where available space is limited. As expected, the silica gel tablets with a higher silica gel content exhibited a higher capacity for water vapor per unit volume. The Grade 11 and Syloid 63 silica gel materials appear to have similar adsorption performance in Tablet form.

Conclusions

The following conclusions can be drawn from the above results:

1) The silica gel tablets had an improved rate of adsorption when compared to the granular silica gel pouch baseline at the conditions tested.

2) The silica gel tablets had much improved capacity for water vapor per unit volume when compared to the granular silica gel pouch baseline at the conditions tested.

3) The capacity of the silica gel for water vapor is unaffected when in tablet form at the conditions tested.

4) There was an insignificant difference in adsorption characteristics between the Davison Grade 11 and Syloid 63 silica gel materials in tablet form at the conditions tested.

Sample 11 PVA or G was compared to P53-7365 baseline. In general, the rate of adsorption for the silicate gel tablet (sample 11 PVA) was greater than the P53-7365 baseline. However the difference in the rate of adsorption for this experiment, as for the other experiments reported above, may have been a result of the fact that the baseline (P53-7365) had a PTFE cover and a different geometry, which could have resulted in a lower surface area to adsorbent mass ratio. In general, the 11 PVA sample, i.e., sample G, adsorbed a greater weight of H2 O, per gram of dry silica gel contained therein. It also adsorbed a greater amount of water per unit volume.

The raw data for this later experiment is reported in Tables V, VI, VII below. Table V shows change of weight, at the time increments. Table VI gives sample specifications concerning masses of silica gel and volume of silica gel in the samples, as well as the pouch weight for the samples which had a pouch. Table VII shows the amount of water vapor adsorbed, at the time intervals.

                                  TABLE V__________________________________________________________________________Raw DataDescription  wt0 wt1 wt2 wt3 wt4 wt5 wt6 wt7 wt8 wt9__________________________________________________________________________P537365 (F)  0.985      1.034          1.065              1.083                  1.101                      1.112                          1.128                              1.134                                  1.140                                      1.164P537365 (F)  1.021      1.074          1.101              1.125                  1.139                      1.152                          1.163                              1.171                                  1.179                                      1.20111 PVA (G1)  2.423      2.507          2.541              2.565                  2.588                      2.598                          2.608                              2.615                                  2.627                                      2.64111 PVA (G2)  2.466      2.542          2.575              2.599                  2.616                      2.628                          2.64                              2.649                                  2.657                                      2.679Time   0   30  60  90  120 150 185 215 255 1030__________________________________________________________________________

              TABLE VI______________________________________Sample SpecificationsSample   Pouch weight                mSG (g)   vSG (cubic inches)______________________________________P537365 (F)    0.236       0.699     0.0699P537365 (F)    0.241       0.730     0.073011 PVA (G1)          0.7008    0.069911 PVA (G2)          0.7176    0.0699______________________________________

                                  TABLE VII__________________________________________________________________________Water Vapor AdsorbedSampleTime   0   30  60  90  120 150 185 215 255 1030__________________________________________________________________________P537365 (F)  0.00       7.01          11.44              14.02                  16.60                      18.17                          20.46                              21.32                                  22.17                                      25.61P537365 (F)  0.00       7.26          10.96              14.25                  16.16                      17.95                          19.45                              20.55                                  21.64                                      24.6611 PVA (G1)  0.00      11.99          16.84              20.26                  23.54                      24.97                          26.40                              27.40                                  29.11                                      31.1111 PVA (G2)  0.00      10.59          15.19              18.53                  20.90                      22.58                          24.25                              25.50                                  26.62                                      29.68__________________________________________________________________________
Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3820309 *Oct 16, 1972Jun 28, 1974Multiform Desiccant Prod IncAdsorbent cartridge
US3918578 *Apr 1, 1974Nov 11, 1975Multiform Desiccant Products IDesiccant end cap
US3953566 *Jul 3, 1973Apr 27, 1976W. L. Gore & Associates, Inc.Process for producing porous products
US4110392 *Dec 17, 1976Aug 29, 1978W. L. Gore & Associates, Inc.Production of porous sintered PTFE products
US4181513 *Apr 26, 1977Jan 1, 1980Toyobo Co., Ltd.Carbon adsorptive filter material with layers of reinforcing non woven fabrics needle punched
US4187390 *Jun 21, 1977Feb 5, 1980W. L. Gore & Associates, Inc.Porous products and process therefor
US4194225 *Jun 6, 1978Mar 18, 1980International Memories, Inc.Housing for disk drive unit
US4217386 *Jun 7, 1979Aug 12, 1980The United States Of America As Represented By The Secretary Of The ArmySpun-bonded, non-woven, polypropylene fabric
US4250172 *Feb 9, 1979Feb 10, 1981Hausheer Hans PNeedled fiber mat containing granular agent
US4272264 *Jul 9, 1976Jun 9, 1981Multiform Desiccant Products, Inc.Adsorbent package
US4308041 *Feb 9, 1981Dec 29, 1981Cambridge Filter Corp.Air filter cartridge
US4418369 *May 4, 1981Nov 29, 1983Miniscribe CorporationMethod and structure for maintaining a low contaminated enclosure
US4453955 *Nov 16, 1982Jun 12, 1984Multiform Desiccants, Inc.Desiccant cartridge for laboratory desiccator
US4471395 *May 17, 1982Sep 11, 1984International Business Machines CorporationSelf-ventilated recirculating airflow system
US4489356 *Jun 24, 1982Dec 18, 1984Atasi CorporationEnclosed disk drive with improved air filtration system
US4581668 *Apr 3, 1984Apr 8, 1986Burroughs Corp.Disk contour cover having air filtration section
US4594626 *Feb 13, 1984Jun 10, 1986Xerox CorporationAir filtration system for rotating disk drives having recirculating air flows
US4600420 *Oct 21, 1985Jul 15, 1986Donaldson Company, Inc.Self-supporting, microscopic particles
US4633349 *Jul 23, 1984Dec 30, 1986International Business Machines CorporationDisk drive air filter assembly
US4636891 *Feb 1, 1983Jan 13, 1987Cii Honeywell BullMagnetic disc cartridge with ventilating structure
US4642715 *Nov 1, 1984Feb 10, 1987Miltope CorporationEnvironmental conditioning and safety system for disk-type mass memories
US4657570 *Mar 20, 1985Apr 14, 1987Donaldson Company, Inc.Air filter device
US4684510 *Dec 20, 1985Aug 4, 1987Hewlett-Packard CompanyChemical filter
US4725904 *Oct 5, 1981Feb 16, 1988Tandon CorporationMagnetic disk memory apparatus with improved contamination control
US4748069 *Jun 20, 1986May 31, 1988Multiform Desiccants, Inc.Liquid absorbing and immobilizing packet and paper therefor
US4751594 *May 22, 1986Jun 14, 1988Magnetic Peripherals Inc.Low diffusion disk drive breather vent
US4772300 *Apr 4, 1985Sep 20, 1988Multiform Desiccants, Inc.Adsorbent cartridge
US4777549 *Oct 14, 1986Oct 11, 1988International Business Machines CorporationSpindle filter in a data recording disk file
US4813791 *Sep 18, 1987Mar 21, 1989Multiform Desiccants, Inc.Bag with integral material treating packets
US4816328 *Nov 13, 1987Mar 28, 1989W. L. Gore & Associates, Inc.Fabric core overcoated with polytetrafluoroethylene
US4830643 *Jul 13, 1988May 16, 1989W. L. Gore & Associates, Inc.Protective covering for adsorbers; dustless, porosity desiccants; air purifiers
US4857087 *Nov 16, 1987Aug 15, 1989International Business Machines CorporationDisk file employing dual filters
US4863499 *Jul 29, 1988Sep 5, 1989Donaldson Company, Inc.Anti-duffusion chemical breather assembly for disk drives
US4877433 *Sep 26, 1988Oct 31, 1989Yoshimi OshitariHigh performance gas filter assembly
US4880448 *Mar 20, 1989Nov 14, 1989Periso Sa Elektro-IndustrieDouble filter insert for an air cleaning apparatus
US4885652 *Jul 11, 1988Dec 5, 1989Minnesota Mining And Manufacturing CompanyDisk cartridge
US4889542 *Nov 14, 1988Dec 26, 1989Hayes William JPolymeric foam panel attached to air intake opening of housing; preventing dust and dirt accumulation
US4911739 *Jul 7, 1989Mar 27, 1990Multiform Desiccants, Inc.Elongated absorbent cartridge
US4947957 *Jun 16, 1989Aug 14, 1990Multiform Desiccants, Inc.Regenerable desiccant cartridge for automotive muffler
US4988903 *Sep 14, 1989Jan 29, 1991Nec CorporationCoil assembly for voice coil motor
US4992410 *Feb 17, 1989Feb 12, 1991Multiform Desiccants, Inc.Oxygen-absorbing package, composition and method of formulation thereof
US5005763 *Jun 14, 1989Apr 9, 1991Multiform Desiccants, Inc.Container for bulk material and method of fabrication thereof
US5009308 *Aug 9, 1989Apr 23, 1991Multiform Desiccants, Inc.Controlled rate adsorbent unit and method of fabrication thereof
US5025336 *Nov 6, 1989Jun 18, 1991Prairietek CorporationDisk drive apparatus
US5029026 *Aug 8, 1989Jul 2, 1991Conner Peripherals, Inc.Disk drive architecture
US5030260 *Dec 4, 1989Jul 9, 1991International Business Machines CorporationDisk drive breather filter
US5034835 *Feb 16, 1990Jul 23, 1991Mitsubishi Denki Kabushiki KaishaDisk drive having air filtration system
US5069694 *Jul 2, 1990Dec 3, 1991Multiform Desiccants, Inc.Permeable envelope of carbon loaded paper containing desiccant, adsorbers, and(or) absorbers
US5075807 *Mar 14, 1990Dec 24, 1991Hitachi, Ltd.Magnetic disk device including humidity controller in disk enclosure
US5081551 *Mar 28, 1989Jan 14, 1992Seiko Epson CorporationRecording and reproducing apparatus
US5092914 *Jun 7, 1990Mar 3, 1992Multiform Desiccants, Inc.Floatable oxygen-absorbing cartridge
US5148337 *Sep 20, 1990Sep 15, 1992Multiform Desiccants, Inc.Controlled rate adsorbent and disc drive stabilizing unit
US5191721 *Sep 30, 1991Mar 9, 1993Multiform Desiccants, Inc.Microwave regenerable desiccant cartridge
US5207943 *Jan 7, 1991May 4, 1993Multiform Desiccants, Inc.Oxygen absorber for low moisture products
US5262375 *May 26, 1992Nov 16, 1993Multiform Desiccants, Inc.Oxygen absorber
US5308703 *Nov 25, 1991May 3, 1994Osaka Gas Company LimitedPurification, decoloring, deodorizing
US5322701 *Jan 14, 1993Jun 21, 1994Multiform Desiccants, Inc.Carbon dioxide absorbent packet and process
US5406431 *Oct 27, 1993Apr 11, 1995Maxtor CorporationFilter system for type II HDD
US5417743 *Jan 21, 1994May 23, 1995W. L. Gore & Associates, Inc.Purifiers for sensitive instruments
US5443626 *Sep 28, 1994Aug 22, 1995Multiform Desiccants, Inc.Fluid collecting device for collecting moisture from tanks
US5500038 *Aug 30, 1994Mar 19, 1996W. L. Gore & Associates, Inc.Non-particulating compact adsorbent filter
US5503662 *Mar 29, 1994Apr 2, 1996Multiform Desiccants, Inc.Canister with porous plastic ends
US5538545 *Nov 4, 1994Jul 23, 1996W. L. Gore & AssociatesNonparticulating adsorbent recirculating filter
US5593482 *Apr 7, 1992Jan 14, 1997W. L. Gore & Associates, Inc.Adsorbent assembly for removing gaseous contaminants
DE3915350A1 *May 10, 1989Nov 15, 1990Gore W L & Ass GmbhSealing disc-drive containers by porous hose - filled with moisture- or gas-adsorbent
EP0427490A2 *Nov 5, 1990May 15, 1991Prairietek CorporationDisk drive apparatus
EP0458528A1 *May 16, 1991Nov 27, 1991International Business Machines CorporationData storage device with vapour pressure control system
WO1996006669A1 *Oct 14, 1994Mar 1, 1996Gore & AssAn improved non-particulating compact adsorbent filter
WO1996014136A1 *Dec 19, 1994May 17, 1996Gore & AssNonparticulating adsorbent recirculating filter
WO1997000717A1 *Jun 19, 1996Jan 9, 1997Donaldson Co IncFilter and method for making a filter
WO1997037756A1 *Mar 11, 1997Oct 16, 1997Gore & AssAn improved clean, stiff, washable, compact adsorbent filter assembly
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US6077335 *Jul 12, 1999Jun 20, 2000Donaldson Company, Inc.Filter and method for making a filter
US6143058 *Dec 9, 1998Nov 7, 2000Donaldson Company, Inc.Adsorbent construction and method
US6146446 *Oct 8, 1998Nov 14, 2000Donaldson Company, Inc.Uses in electronic equipment and chemical manufacturing and storage.
US6168651Jul 14, 1999Jan 2, 2001Donaldson Company, Inc.Filter assembly with shaped adsorbent article; and devices and methods of use
US6196708May 14, 1998Mar 6, 2001Donaldson Company, Inc.Such as a filter or film, formed by contacting a laminate having an expanded polytetrafluoroethylene and porous support scrim with an oleophobic treatment agent comprising a fluoropolymer dissolved in a fluorine-free organic solvent
US6214095Jul 6, 1999Apr 10, 2001Donaldson Company, Inc.Non-adhesive nonporous base layer having a non-adhesive outer surface, adhesive layer disposed on base layer opposite outer surface, non-adhesive filtering layer, adsorbent material; for insertion into internal enclosure of disk drive
US6238467 *Sep 24, 1999May 29, 2001Gore Enterprise Holdings, Inc.Rigid multi-functional filter assembly
US6296691Nov 4, 1999Oct 2, 2001Gore Enterprise Holdings, Inc.Multi-functional molded filter for removing contaminants from an enclosure
US6302934 *Nov 9, 1999Oct 16, 2001Nitto Denko CorporationSemiconductor clean room filters
US6356407 *Mar 31, 1999Mar 12, 2002Seagate Technology LlcSystem and process for reducing contamination in internal disc drive environment
US6395073 *Aug 23, 2000May 28, 2002Gore Enterprise Holdings, Inc.Multi-functional filter for removing contaminants from an enclosure
US6582113Mar 5, 2001Jun 24, 2003Donaldson Company, Inc.Oleophobic laminated articles, assemblies of use, and methods
US6671303 *Jun 10, 2002Dec 30, 2003Coherent, Inc.Purging to extract gas, decomposing ozone; also containing dessicant, organic vapor trapping material and particulate filter
US6709498 *Aug 16, 2001Mar 23, 2004Donaldson Company, Inc.Filter construction for disk drives
US6798813Jul 9, 2001Sep 28, 2004Coherent, Inc.Closed-loop purging system for laser
US7014690 *Dec 18, 2003Mar 21, 2006Westinghouse Air Brake Technologies CorporationExpandable desiccant element
US7083804 *Jan 23, 2001Aug 1, 2006Multisorb Technologies, Inc.For use in computer and electronic devices; for absorbing acid gases from an electronic device
US7125433Dec 31, 2003Oct 24, 2006Donaldson Company, Inc.Dual diffusion channel filter
US7166142Dec 31, 2003Jan 23, 2007Donaldson Company, Inc.Filter constructions containing breather and recirculation filter elements
US7239656Aug 12, 2004Jul 3, 2007Coherent, Inc.Closed-loop purging system for laser
US7404836 *May 11, 2004Jul 29, 2008Donaldson Company, Inc.Focused flow filter
US7862646Jul 30, 2008Jan 4, 2011Advanced Technology Materials, Inc.Nanoporous articles and methods of making same
US7951225May 3, 2006May 31, 2011Advanced Technology Materials, Inc.Fluid storage and dispensing systems, and fluid supply processes comprising same
US7972421 *Mar 10, 2009Jul 5, 2011Advanced Technology Materials, Inc.Rectangular parallelepiped fluid storage and dispensing vessel
US8002880Feb 24, 2009Aug 23, 2011Advanced Technology Materials, Inc.Gas storage and dispensing system with monolithic carbon adsorbent
US8033304Jul 13, 2008Oct 11, 2011Donaldson Company, Inc.Contaminant control filter with fill port
US8053376 *Jun 26, 2009Nov 8, 2011Georgia Tech Research CorporationOne-step synthesis and patterning of aligned polymer nanowires on a substrate
US8116029 *Nov 10, 2008Feb 14, 2012Donaldson Company, Inc.Contaminant-control material for use in an electronic enclosure
US8159778Apr 6, 2009Apr 17, 2012Hitachi Global Storage Technologies, Netherlands B.V.Hard disk drive contamination control
US8221532Jan 4, 2011Jul 17, 2012Carruthers J DonaldNanoporous articles and methods of making same
US8282023May 31, 2011Oct 9, 2012Advanced Technology Materials, Inc.Fluid storage and dispensing systems, and fluid supply processes comprising same
US8282714Aug 23, 2011Oct 9, 2012Advanced Technology Materials, Inc.Gas storage and dispensing system with monolithic carbon adsorbent
US8506689Jun 26, 2011Aug 13, 2013Advanced Technology Mateials, Inc.Rectangular parallelepiped fluid storage and dispensing vessel
US8539781Jun 22, 2008Sep 24, 2013Advanced Technology Materials, Inc.Component for solar adsorption refrigeration system and method of making such component
US8679231Dec 17, 2011Mar 25, 2014Advanced Technology Materials, Inc.PVDF pyrolyzate adsorbent and gas storage and dispensing system utilizing same
WO1999058335A1 *May 14, 1999Nov 18, 1999Donaldson Co IncOleophobic laminated articles, assemblies of use, and methods
WO2001008784A1 *Aug 2, 2000Feb 8, 2001Thomas BeckenhauerCompositions useful as desiccants and methods relating thereto
WO2001022421A1 *Sep 20, 2000Mar 29, 2001Gore Enterprise Holdings IncImproved multi-functional molded filter for removing contaminants from an enclosure
WO2001041901A1 *Dec 7, 2000Jun 14, 2001Donaldson Co IncAdsorbent assembly comprising polypropylene filtering layer for removing gaseous contaminants
Classifications
U.S. Classification96/13, 96/153, 96/154, 55/385.6, G9B/33.044, 96/135, 55/385.1
International ClassificationC08L101/00, C08K3/36, G11B33/14, B01J20/28
Cooperative ClassificationG11B33/146
European ClassificationG11B33/14C4
Legal Events
DateCodeEventDescription
Sep 2, 2010FPAYFee payment
Year of fee payment: 12
Aug 31, 2006FPAYFee payment
Year of fee payment: 8
Aug 22, 2002FPAYFee payment
Year of fee payment: 4
Nov 17, 1997ASAssignment
Owner name: DONALDSON COMPANY, INC., MINNESOTA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:DAHLGREN, ANDREW CHRISTIAN;ROGERS, ROBERT MURRAY;REEL/FRAME:008796/0868
Effective date: 19971113